1. Field of the Invention
The present invention relates to a signal processing circuit capable of accessing an external memory.
2. Description of the Related Art
With a signal processing circuit, a memory is externally connected to transmit and receive data to and from the external memory, whereby the data can be processed. In such a system, timing for transmitting and receiving the data between an interface of the signal processing circuit and the external memory needs to be adjusted. At this time, an integrated circuit constituting the signal processing circuit has fluctuation in characteristics, and hence the timing with respect to the external memory is adjusted for each signal processing circuit.
However, with increased speed of the data processing, increased speed of access between the interface of the signal processing circuit and the external memory is also required, and it becomes difficult to adjust the timing of the access.
For example, even in a case where the timing with respect to the external memory can be adjusted from the viewpoint of design of the signal processing circuit, it sometimes becomes difficult to adjust the timing of the access to the external memory owing to an influence of actual layout of the circuit. Fluctuation in characteristics of the respective external memories similarly influences the timing adjustment.
Furthermore, the layout of a substrate on which the signal processing circuit and the external memory are mounted, fluctuations of other external peripheral devices and a power circuit, and the like, influence the timing adjustment of the access between the signal processing circuit and the external memory.